Methods have been devised for dispensing mercury or other materials with high vapor pressure characteristics into a gas-filled discharge tube such as a fluorescent lamp. Typically, the mercury or a like material is inserted into a capsule or ampule and the capsule is then inserted into the envelope of the tube. At the desired moment during the manufacturing process, mercury is released by opening the ampule. See, for example, U.S. Pat. No. 3,684,345 and U.S. Pat. No. 4,534,742.
Recently it has been determined that the efficiency of low pressure mercury-rare gas discharge lamps can be enhanced if the isotopic mixture of the mercury is changed from that which occurs naturally. See, for example, Electric Discharge Lamps, MIT Press, 1971, by J. Waymouth for basic principles of low pressure mercury rare gas discharge lamps and U.S. Pat. No. 4,379,252. This patent teaches efficiency gains in fluorescent lamps when the .sup.196 Hg isotope is increased from its natural occurrence of about 0.14% to about 3%.
The problem of employing such altered compounds of mercury lies in their expense. For example, at current prices, mercury which has been enhanced to contain 35% of the .sup.196 Hg isotope costs about $500/milligram (mg). Accordingly, it can be seen that the use of this material requires very strict controls on the amount employed. Further, such materials need only be used in milligram or submilligram amounts. It has been very difficult to dispense such precise and accurate amounts of Hg into devices which require mercury. It is particularly difficult when the amount of mercury required is in milligram or submilligram amounts.